Biology: Zoology: UPSC Previous Year Questions (Science and Technology)

Explanation

Genetic disorders are caused by abnormalities in an individual’s DNA, inherited from parents or arising from mutations. They can affect structure, function, or production of proteins. Types include single-gene disorders (e.g., cystic fibrosis), chromosomal disorders (e.g., Down syndrome), and multifactorial disorders (e.g., diabetes), impacting health, development, or metabolism.

Option (d) is correct:

Color blindness is a sex-linked recessive disorder carried on the X chromosome. In the above case, the woman suffers from color blindness but her husband does not. Woman’s Genotype: Since the woman has color blindness, her genotype must be X^cX^c (as both X chromosomes carry the color blindness allele). Man’s Genotype: Since the man does not have color blindness, his genotype must be XY (as the Y chromosome does not carry the color blindness gene). Children’s Genotypes:

Son: A son inherits his X chromosome from his mother and his Y chromosome from his father. Since the mother has the X^c chromosome, the son’s genotype will be X^cY, meaning the son will suffer from color blindness. Daughter: A daughter inherits one X chromosome from her mother and one X chromosome from her father. Since the father has a normal X chromosome, the daughter’s genotype will be X^cX. Since color blindness is a recessive trait, the daughter will be a carrier but won’t suffer from color blindness.

Explanation

The flying fox is a type of megabat belonging to the Pteropus genus in the Pteropodidae family. These large bats have wingspans ranging from 1.5 to 1.8 meters and are known for their fox-like faces, which is how they got their name. Flying foxes are found mostly in tropical and subtropical areas, particularly in coastal regions and tropical forests of India. As frugivores, they primarily feed on fruit and play a vital role in pollination and seed dispersal, contributing to the health of their ecosystems. Unlike smaller insect-eating bats, flying foxes do not rely on echolocation. Instead, they use their sharp vision to navigate and find food. This makes them unique compared to other bat species.

Explanation

Salamander-Python-Kangaroo sequence follows a correct evolutionary progression:

Salamanders are amphibians to the class Amphibia.

Amphibians evolved from fish and are characterized by their ability to live both in water (as larvae) and on land (as adults). Pythons are reptiles in the class Reptilia which have evolved from amphibians. Reptiles are vertebrates with dry skin, and they lay eggs on land (as opposed to amphibians, which generally need water for reproduction). Kangaroos are mammals, specifically marsupials in the class Mammalia. Mammals evolved from reptiles. Kangaroos are one of the few mammals that give birth to underdeveloped offspring, which then continue to develop in a pouch.

Explanation

The giant panda (Ailuropoda melanoleuca) belongs to the Ursidae family, which includes all modern bears such as grizzly, polar, and black bears. Though classified as carnivores, giant pandas are mainly herbivores, with bamboo making up to 99% of their diet. They have a unique "thumb" (modified wrist bone) that helps them grasp bamboo. These solitary creatures are recognized by their black and white fur and have a slow metabolism due to their low-calorie diet. Pandas are found in the mountainous regions of China and are classified as vulnerable because of habitat loss and low reproductive rates. Females are only fertile for a few days each year, making reproduction difficult. Conservation efforts have helped increase their population. The giant panda is a symbol of wildlife conservation and through panda diplomacy, it has helped strengthen diplomatic ties between China and other countries. IUCN Status: The IUCN Red List (International Union for Conservation of Nature) currently classifies the giant panda as Vulnerable.

Explanation

The Dugong (Dugong dugon) is a marine mammal found in shallow coastal waters of the Indo-Pacific. It is closely related to manatees. The dugong has a torpedo-shaped body with a fluked tail (similar to a whale’s) and two front flippers. Its skin is grayish-brown, and it has a rounded, wrinkled face that helps it forage for seagrass, its primary food source. Dugongs can grow up to 3 meters in length and weigh up to 400 kg. Dugongs are herbivores and feed mainly on seagrass, earning them the nickname "sea cows". They play a crucial role in maintaining healthy seagrass ecosystems. However, dugongs are vulnerable due to habitat loss, hunting, bycatch, and seagrass degradation. Conservation efforts focus on protecting their habitats through marine protected areas and reducing fishing gear entanglements.